1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to a sigma-delta modulator and an analog-to-digital (A/D) converter using the same, and more particularly, to a sigma-delta modulator capable of reducing quantization noise and an A/D converter using the same.
2. Description of the Related Art
Most of the signals in the natural world continuously change with time. In order to understand a phenomenon in the natural world, it is necessary to measure analog signals that continuously change with time. Also, the measured values may be processed and analyzed through a computer. In order to process and analyze the analog signals through a computer, a device is required for converting the analog signals into digital values which can be processed by the computer. Such a device is called an analog-to-digital (A/D) converter.
Among A/D converters, a sigma-delta A/D converter has been widely used for its advantages of high definition and a high level of circuit integration achieved at low cost.
The sigma-delta A/D converter and a sigma-delta modulator included in the sigma-delta A/D converter calculate a digital signal as a final output using an oversampling technique.
However, the oversampling technique may cause quantization noise in addition to generation of a desired signal. The quantization noise has a tendency to gradually increase as a frequency increases.
In discriminating and detecting a desired signal component from quantization noise, a small average noise floor of the quantization noise is more advantageous.